Watch this, I've done this only to get some smoke from excessive splash via the rods bearings, took the washer back out. Sadly there's no room to pull the pan in a sedan like you can in a Power Wagon, I rebearinged a wideblock in a '65 W200, did wonders for oil pressure and start up noise all gone.
These cars were designed around 180º thermostats, 210º seems a tad bit hot and contributes to the low oil pressure warm.
Once it's broke in to your liking, Power Punch or Lucas will increase viscosity index for better idle oil pressure, good coating for startups, clingy.
Had a GF with 300ZX that had run out of oil, filled it up with Power Punch, noisy as hell but it got her to work everyday, the motor had 0 psi at idle warm. Based on her looks I could she could get a very decent trade in on the car in that condition and she did.
UPDATE! Timing now advanced back to canonical 12.5 BTDC, replaced wonky distributor with good one. (Wonky had bad upper bushing.) Runs 100% better now. Come summer, I still am apt to seek a cooler running plug, but with running temp down to 198-205 in traffic, and a slightly more viscous oil, minimum warm idle oil pressure now at a healthy 15-20 psi. Trudi once again idles so butter smooth, folks have to ask if it's running. (This even occurred in August, at the Emissions testing station, BEFORE the head upgrade! See note below on plug wires.)
The only time idle now ever is noticeable is on the cooler mornings, I have to pull the choke a bit for a couple minutes if starting from ambient sub 50 F temperature.
Note, once I ditched the crap suppressor plug wires insisted on by the Chebbie Chimp, and went back to my Packard 440 + Rajah terminals home rolled ones. idle improved yet again, to a degree I didn't think attainable with this old motor.